Testing machine having grip mechanism



June 6, 1967 w. T. GLOOR 3,323,357

TESTING MACHINE HAVING GRIP MECHANISM 7 Filed June 4, 1964 I 5 Sheets-Sheet 1 UK Z7 Z6 Z I Z0 Q 29 z I I g 3/ 26 25 l E 52 35 "M50: 1: 4% Z J j I Z I 1L0 |Z t (\JTT! L F? o ,e/ l; 2/

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INVENT R /4 /wr 7. 6' par ATTORNEY3 June 6, 1967 w, GLOOR 3,323,357

TESTING MACHINE HAVING GRIP MECHANISM Filed June 4, 1964 3 Sheets-Sheet 2 a, a V a; 15

/ I INVENT R 1/1/110'716' oar ATTORNEY-5' United States Patent 3,323,357 TESTING MACHINE HAVING GRIP MECHANISM Wilbur T. Gloor, Berwyn, Pa., assignor, by mesne assignments, to The Warner & Swasey Company, Cleveland, Ohio, a corporation of Ohio Filed June 4, 1964, Ser. No. 372,544 4 Claims. (Cl. 73103) The present invention relates to testing machines and particularly to power grips therefor.

The purpose of the invention is to provide a testing machine with power grips which clamp under a force which is proportional to the load on the testing machine.

A further purpose is to provide a combination of movable and fixed grips for a testing machine and to energize the movable grips under a force which is proportional to the highest load applied by the testing machine in making a test, whether this is a load in tension or compression or otherwise.

A further purpose is to interpose between a main hydraulic system for moving the heads of a testing machine and hydraulic means for operating movable grips, an intensifier which will energize the grips in proportion to the pressure in the main hydraulic system.

A further purpose is to mount the grips on a C-shaped housing with the open portion of the C directed to the front to improve the accessibility of the specimen.

A further purpose is to provide a longitudinal bearing on the grip housing for each relatively fixed grip extending in the direction of relative motion of the heads and also a transverse bearing for each relatively fixed grip extending transverse to the direction of relative motion of the heads at a side toward which the relatively fixed grip pulls in making a test, and to provide on the relatively fixed grip a longitudinal bearing portion acting against the longitudinal housing bearing and also a transverse bearing portion acting against the transverse housing bearing.

A further purpose is to provide a shim between the longitudinal housing bearing and the longitudinal bearing portion on each relatively fixed grip to permit aligning the relatively fixed grips.

A further purpose is to provide on the means for moving the relatively movable grips a longitudinal hearing for said relatively movable grip extending in the direction of relative motion of the heads, and also a transverse bearing for the relatively movable grip extending transverse to said direction of relative motion of said heads at a side toward which said relatively movable grip pulls in making a test, and to provide the relatively movable grip with a longitudinal bearing portion acting against this longitudinal bearing and also with a transverse bearing portion acting against said transverse bearing.

A further purpose is to apply continuously to each grip a pressure proportional tothe main cylinder pressure which can develop a clamping load on the specimen of the order of 20% or more greater than the axial specimen load as developed by the main cylinder pressure.

Further purposes appear in the specification and in the claims.

In the drawings I have chosen to illustrate a few only of the numerous embodiments in which the invention may appear, selecting the forms shown from the standpoints of convenience in illustration, satisfactory operation, and clear demonstration of the principles involved.

FIGURE 1 is a front elevation partly broken away showing a typical tensile testing machine to which the grips of the invention have been applied.

FIGURE 2 is a plan section of FIGURE 1 on the line 22.

FIGURE 3 is a front elevation partly broken away showing the upper power grip illustrated in FIGURES l and 2 to enlarged scale.

FIGURE 4 is a top plan view of the upper power grip of FIGURE 3.

FIGURE 5 is a right end elevation of FIGURE 3.

FIGURE 6 is a hydraulic schematic diagram for the iystersn for operating the testing machine of FIGURES FIGURE 7 is a diagrammatic view showing the principles of the invention applied to a universal testing machine for testing materials in tension and compression.

Describing in illustration but not in limitation and referring to the drawings:

In the prior art, the grips which hold the specimen in a testing machine have, in the main, been manually actuated. Considerable skill by the operator has been required to avoid applying too much pressure so as to crush the specimen and fail to obtain a satisfactory test,

a or too little pressure so that the specimen will pull out of the grips.

An important advantage of the device of the invention is that the force applied to the grips is made proportional to the load under which the specimen is being tested, and in the preferred embodiment, is made proportional to the highest load subjected to the specimen during the test.

The improved grips of the invention are preferably contained in C-shaped housings, making the grips and the specimen more accessible.

For mounting the fixed grips, the housings are pro vided with longitudinal bearings extending in the direction of relative movement of the heads of the testing machine and also transverse bearings extending at right angles thereto on the side of the housings toward which the specimen pulls when load is applied, and the fixed grips have corresponding longitudinal and transverse bearing portions which engage these bearings. Thus,'the anchorage of the relatively fixed grips is very strong and not likely to fail by shear.

Similarly, the mechanism which moves the relatively movable grips has longitudinal and transverse bearings and the relatively movable grips have corresponding longitudinal and transverse bearing portions which firm- 1y mount the relatively movable bearings In the case of a universal testing machine, the force applied to the grips corresponds to the highest pressure applied during the test either on the tension side or on the compression side.

Considering now the drawings in detail, the'tensile testing machine of the invention has on the two sides of the machine vertical rods 20- and 21 which are crossconnected at the bottom by the bed of the machine, not shown, and at the top by a loading head 23, shown.

Guided on the rods 20 is a loading head 23 and guided on the rods 21 is a weighing head 24, as well known in the art. The details of the mechanism for applying load to the loading head and for measuring the load on the weighing head are not important to the present invention and this mechanism has been Omitted.

Each of the heads has extending in the longitudinal direction a bore 25 through which a threaded stud 26 extends and the stud is held by a locking nut 27 in a nut recess 28.

Each of the grips is spaced with respect to the head 23 or 24 by a resilient washer 32 suitable for absorbing shock of specimen failure.

Considering particularly FIGURES 3, 4 and 5, each of the grips 33, which are suitably merely opposite counterparts, comprises a grip housing 34 which is of C Patented June 6, 1967 3 formation, best seen in FIGURE 3, having one arm of the C at 35, another arm of the C at 36 and an open front 37.

At the end adjoining the head of the machine to which the grip is to be secured, the housing has a threaded opening 38 extending in the longitudinal direction which receives the threaded stud 26 to. support the housing.

The housing has at the side 35, which is to receive the fixed grip, a longitudinal bearing 40 extending in the direction of relative motion of the heads. At the side of the head toward which the fixed grip will pull there is a transverse bearing 41 which is extending in a direction transverse to the direction of relative motion of the heads.

It is important to be able to load the upper and lower fixed grips precisely with respect to one another and so the longitudinal bearing 40 is engaged by one surface to a shim or spacer 42, which is one of a series of variable thickness and has on its longitudinal surface a bearing 43 parallel to the bearing 40. The shim extends to an accessible point and has an opening 42' serving as a finger-hold or a hook engaging opening to permit removing the shim.

The relatively fixed grip 44 is of L-shape, having a longitudinal bearing portion 45 which engages longitudinal bearing 43 on the shim and also has a transverse bearing portion 46 which engages the transverse bearing 41 on-the housing. The housing 34 also has a transverse bearing 47 which engages anopposite transverse bearing portion 48 on the grip.

The relatively fixed grip is held in place by a screw 50 passing through an opening 51 in the housing, threading into an opening 52 in the relatively fixed grip. A handle 53 is provided on the outer end of the screw 50. The relatively fixed grip itself also has a handle 54 which is accessible at the front of the machine, as shown in FIG- URE 3, to permit removal.

The relatively fixed grip 44 has a friction face 55 secured by screws 56 and replaceable, as desired. The shims 42 are positioned and held in place by providing them with pins 57- which engage in openings 58 in the longitudinal bearing 40.

At the opposite side 36 of the C housing, and extending in the direction transverse to the direction of longitudinal relative movement of the heads, there is a hydraulic cylinder 60, composed of a cylinder housing 61 integral with the grip housing, and a suitably honed cylinder liner 62 sealed to the cylinder housing by a suitable packing 63. The cylinder liner is held in place by a cylinder. head 64, sealed by a packing 65 held to the cylinder by bolts 66 and having a port 67 for connection to the hydraulic system to be described.

The cylinder is double acting, and has a hydraulic connection 68 to the opposite end.

Coaxial with the cylinder is a reduced bore 70 for sealing to and guiding a piston 71, sealed by packing 72. The piston 71 is integrally connected to an enlarged piston portion 73, sealed by a packing 74 and riding in the cylinder 60 provided by the cylinder liner 62.

The piston 71 has at its end toward the specimen, a longitudinal bearing 75 extending in the direction of relative motion of the heads of the testing machine and also has a transverse bearing 76 on the side of the piston toward which the grip will pull when load is applied. The piston also has a key-recess 77 into which a key portion of the movable grip can engage, as later explained.

The movable grip has a longitudinal bearing portion 78 which engages the longitudinal bearing 75 and also a transverse bearing portion 80 which engages the transverse bearing 76 and a key 81 which fits into the keyrecess 77 behind the transverse bearing 76 and locks against longitudinal-pull downward in FIGURE 3.

The housing also has a transverse bearing 82 which engages a transverse bearing portion 83 on the L-shaped grip at the top in FIGURE 3.

The movable grip has a specimen-engaging portion 84 which is replaceable and is held by screws 85. The movable grip also has a handle 86 accessible for removal. It is locked in the front and back direction by a spring detent 87 in the front of the piston 71 which engages a detent opening 88 in the movable grip.

It will be evident that the housing makes a self-contained unit in which the grips are mounted and they can be applied to existing machines by simply removing the old grips and fastening with the stud above referred to. The grip housing acts like a casing which encloses the components and protects them.

The grip clamping load is applied by pressure through port 67 which enters chamber 90' and is applied to the large end of piston 73.

The piston is double acting and has a retracting chamber 91 to which hydraulic pressure is applied to retract it when the specimen is removed.

The piston has a radially extending pin 92 which rides in a slot 93 in the piston housing to prevent rotation of the piston.

The specimen is maintained in central position in the grip assembly by a gauge plunger 94, moving in a gauge housing 95 aligned by detent 96, the plunger being threaded at 97 to engage a nut 98 riding in a slot 100 in the gauge housing.

The grip housing 34 has ribs 101 which prevent serious deflection under combined stresses.

Referring to the hydraulic system shown in FIGURE 6 and which is intended insofar as it relates to the main hydraulic system to be any suitable hydraulic system for the purpose, pump 102 draws hydraulic liquid from a sump 103 and discharges it through two-way valve 104 to the main hydraulic cylinder for applying load to loading head 23, as indicated by arrow 104. During retraction when the valve is thrown to the opposite position hydraulic liquid returns to the sump through connection 105.

While it is not intended to restrict to a particular form of pump, I show a valve 106 in the line 107 to the main hydraulic system which is connected at opposite sides by lines 108 and 110 to a stroking control device 111 as well known.

For the purposes of operating the grips in proportion to the maximum load applied on the main hydraulic system of the testing machine, the pressure side of the main pump 102 has connected to it a line 112 which extends through a check valve 113 to a line 114 which includes a flexible connection 115 and branches to connect to a line 116 for supplying pressure to the upper grip, and a line 117 having a flexible connection 118 for supplying pressure to the lower grip as will be described. A safety valve 120 is provided to relieve excess pressure above that which the pump can stand by passing hydraulic liquid through line 121 back to the sump.

The check valve 113 is arranged to pass hydraulic liquid, suitably oil, into the connection 114 but it prevents reverse flow and loss of pressure in the system. Pressure enters the line 114 on increasing loads only and hence the specimen remains clamped at the highest pressure developed, and the clamping pressure will not be released if the power fails or if the pump pressure is released. This is an important safety precaution.

In the particular machine described, the upper unit moves upward for tension testing and the pressure and return lines from the upper unit pass through flexible connections to the lower unit which are carefully arranged so that Bourdon effect of changes in pump pressure result in small cross loads on the lower weighing head instead of vertical loads which would affect the precision of'the weighing system.

Both the upper and lower grips have selector valves 122 manually controlled by handles 123 (FIGURE 6 and FIGURES l and 2). Each of the selector valves 122 has three positions as shown diagrammatically, position 124, 125 and 126. Position 124 as shown in the diagram passes fluid pressure from line 116 or line 117 to line 127 which connects to a prefill port 128 of an intensifier or pressure booster 130 to be described. The intensifier has a large cylinder 131 which has in it a large piston 132 which is interconnected with a small ram 133 guided in a bore 134 and extending into a small cylinder 135 which has at one end a prefill chamber 136 connected to the prefill port 128 previously described. If the small ram 133 moves far enough it encounters annular sealing walls 137 closing off the prefill port 128 and beyond the sealing walls 137 it enters a chamber portion 138 which is connected by piping connection 140 to the space 90 in grip operating cylinder 60.

Also, when the selector valve is in position 124, it provides a connection from chamber 91 on the retracting end of cylinder 60 through pipe connection 141 to the chamber around the small piston 133 and then through pipe connection 142 to the selector valve 122 and through the selector valve through pipe connection 143, and in the case of the lower grip through flexible connection 144 to pipe connection 145, flexible connection 146 and pipe connection 121 to the sump.

Thus in efiect when the selector valve is in position 124 it closes the grips and clamps the specimen. Since the areas on the two sides of piston 132 are dilferent, a higher pressure is applied to space 90 in grip cylinder 60 than that which is applied in the main hydraulic system. A sequence valve 147 is connected to high pressure line 127 to prevent pressure from entering the low pressure chamber 148 in the intensifier or pressure booster until chamber 90 in grip clamping cylinder 60 is prefilled. The sequence valve of type well known in the art has a pressure setting determined for example by spring 150 which prevents flow through it until a predetermined pressure is reached, after which flow takes place from the main pressure line 127 and pipe 151 through sequence valve 147 into the booster chamber space 148 via pipe 152.

The sequence valve 147 also has, in piping 153 bypassing it, a check valve 154 which permits reverse flow to occur when required. The sequence valve 147 has a drain line 155 provided to remove any leakage.

When each of the selector valves 122 is in position 125, the high pressure line 114 and also the return line 145 are cut off. Piston 133 stops under these conditions.

When selector valve 122 is in position 126, the high pressure lines 127 is connected to the retracting chamber 91 and the return line 142 is connected to the chamber 90 so that the grips release the specimen.

A suitable ratio of intensifier or booster areas between the piston area exposed to chamber 148 and the piston area exposed to chamber 156 is chosen to properly intensify the hydraulic liquid pressure in chamber 90.

When chamber 148 receives pressure, the ram 133 moves forward to seal off the connection to high pressure line 127 by closing seal 137 and chamber 90 is then subjected to a pressure which is in direct ratio to the pressure of pump 102 as the piston area exposed to the chamber 148 bears to the area .at the end of the ram 133.

When the selector valve 122 is in the position 126, the pressure of the pump 122 is directed to chambers 156 and 91. Chamber 148 and connection 127 are connected to the oil return line 145. Chamber 90 exhausts to chamber 138 and then to line 127 when the ram 133 passes seal 137.

The selector valve 122, the sequence control valve 147 and the intensifier 128 will suitably be commercially available units well known in the art for other purposes.

In some cases where the testing machine is intended for universal use, that is to test both tension and compression, and the grips are suitably designed for this purpose, it is desirable to make a slight modification in the system as shown in FIGURE 7. Here a reversible pump 102 withdraws oil through one connection 161 and pumps it out through another connection 162 or vice versa. A double acting main system cylinder 163 has a piston 164 connected to opposite rams 165 and 166.

6 Depending on whether the machine is operating in tension or compression, the pump 102 will act in one direction or the reverse direction as suggested by double arrow 167.

The opposite chambers 168 and 170 at opposite sides of the piston are connected to lines 114' and 114 each of which has therein a check valve 113 which discharges into a line 114 as shown in FIGURE 6. Thus it will be evident that the grips respond to Whichever is the higher pressure and if the compression load is higher than the tension load they will respond to the compression load pressure rather than the tension load pressure.

Operation In operation of the device of the invention, the selector valves 122 for both grips are moved to position 126 causing opening of the grips as previously explained. The gauge 94 is adjusted to properly position the specimen laterally. The testing machine heads are moved relative to one another to provide the desired spacing for the particular specimen. The specimen is then placed in the space between the grips, and the selector valves 122 are manually moved to positions 124, first causing high pressure hydraulic liquid from the pump 102 to flow in each grip through connection 114 and connection 127 and port 128, chamber 138 and connection 140 to prefill chamber 90. When the pressure builds up to an adequate level to permit sequence valves 147 to open, high pressure liquid enters chambers 148 and begins to force pistons 132 forward while discharging hydraulic liquid from chambers 156. As soon as rams 133 encounter and close at seal 137 the intensifiers begin to act to produce higher pressure in the chambers 138 than that in the chambers 148 according to the ratio of the areas. This high pressure fluid then enters chambers of cylinders 60 while fluid from the opposite ends of cylinders 60, that is in chambers 91, is discharged to the sump. The grips then engage and hold the specimen. As the load increases, the pressure in connection 114 builds up and correspondingly the gripping force increases always in the ratio of the areas of the intensifiers.

If at any time the hydraulic pressure in the main system drops off, because the load on the specimen decreases or because of a power failure or otherwise, the grips cannot release because of the action of check valve 113.

When it is desired simply to hold without releasing, the selector valves are moved to positions 125.

When it is desired to release the grips, the selector valves are moved to positions 126, causing the high pressure liquid to enter retraction chambers 91 in grip cylinders 60, while the opposite chambers 90 are connected to the sump as soon as the intensifier rams 133 pass seals 137.

In view of my invention and disclosure, variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art to obtain all or part of the benefits of my invention without copying the structure shown, and I, therefore, claim all such insofar as they fall within the reasonable spirit and scope of my claims.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. In a testing machine, relatively movable heads, hydraulic means for moving the heads relative to one another including a main hydraulic system, grip means operatively connected to the heads, each grip means including relatively movable grips and hydraulic means for relatively moving the grips, in combination with hydraulic means responsive to the pressure in said main hydraulic system for energizing said hydraulic means for relatively moving the grips at a pressure which increases with the pressure in the main hydraulic system.

2. A testing machine of claim 1, in combination with means for maintaining on said hydraulic means for moving the grips, a pressure proportional to the highest pressure applied to said main hydraulic system during a particular test.

3. A testing machine of claim 1, in which said hydraulic means responsive to the pressure in said main hydraulic system comprises an intensifier having input connection to the main hydraulic system and output connection to the hydraulic means for relatively moving the E. In a testing machine, relatively movable heads, hydraulic means for relatively moving said heads for applying either tension or compression to a specimen, including a main tension hydraulic system and a main compression hydraulic system, grip means operatively connected to the heads, each grip means including relatively movable grips and hydraulic means for relatively moving the grips, in combination with hydraulic means responsive to the highest pressure attained in said main References Cited UNITED STATES PATENTS 2,419,711 4/1947 Dillon 731O3 X 2,425,931 8/1947 Golick 73-103 X 2,597,404 5/1952 Teske.

2,908,163 10/1959 McClelland 73-103 RICHARD C. QUEISSER, Primary Examiner.

J. W. MYRACLE, Assistant Examiner. 

1. IN A TESTING MACHINE, RELATIVELY MOVABLE HEADS, HYDRAULIC MEANS FOR MOVING THE HEADS RELATIVE TO ONE ANOTHER INCLUDING A MAIN HYDRAULIC SYSTEM, GRIP MEANS OPERATIVELY CONNECTED TO THE HEADS, EACH GRIP MEANS INCLUDING RELATIVELY MOVABLE GRIPS AND HYDRAULIC MEANS FOR RELATIVELY MOVING THE GRIPS, IN COMBINATION WITH HYDRAULIC MEANS RESPONSIVE TO THE PRESSURE IN SAID MAIN HYDRAULIC SYSTEM FOR ENERGIZING SAID HYDRAULIC MEANS FOR RELATIVELY MOVING THE GRIPS AT A PRESSURE WHICH INCREASES WITH THE PRESSURE IN THE MAIN HYDRAULIC SYSTEM. 